The prevalence, anatomic distribution, and diagnosis of colonic causes of chronic diarrhea.

BACKGROUND: The prevalence of chronic diarrhea from a colonic disease and the optimal method of its diagnosis have not been ascertained.

METHODS: Eight hundred nine patients with chronic non-bloody diarrhea unassociated with human immunodeficiency virus (HIV) infection underwent colonoscopy with biopsy specimen taken from throughout the colon and, if reached, the terminal ileum. The prevalence and anatomic distribution of ileocolonic histopathology and whether flexible sigmoidoscopy or colonoscopy represents the safest and most cost-effective test for diagnosis were determined.

RESULTS: 122 of 809 patients (15%) had colonic histopathology (microscopic colitis in 80 patients, Crohn's disease in 23, melanosis coli in 8, ulcerative colitis in 5, other forms of colitis in 5, and nodular lymphoid hyperplasia in 1). A correct assessment of colonic histology (normal or abnormal) could have been made from biopsies of the distal colon in 99.7% of patients.

CONCLUSION: In a referral setting, colonic histopathology occurs in 15% of patients with chronic diarrhea without HIV infection. According to this prevalence and the nearly universal diffuse anatomic distribution of colonic disease in these patients, a diagnostic investigation for chronic colonic diarrhea using a 60 cm flexible sigmoidoscope is highly efficient and cost-effective.